Planar resonator and filter

Abstract

The invention discloses a planar resonator and a filter, and belongs to the technical field of electronic communication. The planar resonator is manufactured on the circuit substrate and is composed of two metal strips with the length of 1 / 4 lambda to 1 / 12 lambda, namely a first metal strip and a second metal strip which are arranged in parallel in a staggered mode. One end of the first metal strip is connected with the upper metal grounding strip, and the other end is vacant; one end of the second metal strip is connected with the lower metal grounding strip, and the other end is vacant. The resonators are adopted to construct the planar band-pass filter, the inherent size of the planar filter is reduced, the miniaturization design is achieved, a transmission zero point is further introduced through cross coupling between the resonators, the frequency selectivity is improved, higher-level stop-band suppression is achieved, and application in more occasions is met. The design of the planar resonator and the filter can be realized in a microstrip circuit, a strip line circuit and a suspended microstrip circuit, is suitable for the design of a broadband filter and a narrowband filter, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic communications, and in particular relates to a resonator and a filter. Background Art

[0002] In modern communication systems, resonators and filters play a vital role in the transmission and processing of signals. A resonator is an electronic component or device that can produce resonance at a specific frequency and can be used as a key component of filters, oscillators, etc. The filter it constitutes can select signals within a specific frequency range and suppress unwanted frequency signals or interference signals, thereby improving the performance and reliability of the communication system. In the existing technology, resonators and filters can be implemented in a variety of different structures, among which planar resonators and filters have been widely used because of their small size, low cost, and easy integration.

[0003] With the continuous development of communication technology, the performance requirements for traditional planar resonators and filters are becoming higher and higher, such as smaller size to meet miniaturization requirements, lower loss to meet energy saving or long-distance transmission requirements, wider stopband suppression to meet high-quality communication requirements, etc., to adapt to applications in more occasions.

[0004] The present invention aims to provide a planar resonator and filter design technology with small size, high performance and easy integration to meet the development needs of modern communication systems. Summary of the invention

[0005] The present invention discloses a planar resonator with a new structure, such as Figure 1 As shown. By using the resonator to construct a planar bandpass filter, the inherent volume of the planar filter is reduced, a miniaturized design is achieved, and a transmission zero is introduced through cross-coupling between resonators, which improves the frequency selectivity and achieves a higher level of stopband suppression to meet applications in more occasions. The proposed planar resonator and filter design can be implemented in microstrip circuits, stripline circuits, and suspended microstrip circuits, and is applicable to the design of broadband filters and narrowband filters, and has broad application prospects.

[0006] The technical solution of the present invention is a planar resonator, which comprises: a first metal strip (1), a second metal strip (2), an upper metal grounding strip (3), and a lower metal grounding strip (4); the upper metal grounding strip and the lower metal grounding strip (4) are arranged in parallel, the first metal strip (1) and the second metal strip (2) are arranged in parallel and are located between the upper metal grounding strip and the lower metal grounding strip (4), one end of the first metal strip (1) is connected to the upper metal grounding strip (3), and the other end is vacant; one end of the second metal strip (2) is connected to the lower metal grounding strip (4), and the other end is vacant; the overall length of the coupling structure formed by the first metal strip (1) and the second metal strip (2) is 1 / 4λ to 1 / 12λ, where λ is the waveguide wavelength of the resonant frequency of the resonator; because the first metal strip (1) and the second metal strip (2) overlap at most positions, and because the gap (5) between the two is coupled to form a capacitive loading effect, the length of the conventional planar resonator can be shortened.

[0007] Furthermore, the upper metal grounding strip (3) and the lower metal grounding strip (4) are grounded through metallized vias (6).

[0008] A planar bandpass filter using the planar resonator, such as Figure 2-Figure 5 The filter comprises: a plurality of planar resonators, an input feeder (7), and an output feeder (8); each resonator shares a same upper metal grounding strip (3) and a same lower metal grounding strip (4); the upper metal grounding strip (3) is parallel to the lower metal grounding strip (4); the input feeder (7) is connected to the first-stage planar resonator by means of a tap or coupling, and the output feeder (8) is connected to the last-stage planar resonator by means of a tap or coupling.

[0009] Furthermore, the input feed line (7) is connected to the metal strip outside the first-stage planar resonator by means of a tap or coupling, and the output feed line (8) is connected to the metal strip outside the last-stage planar resonator by means of a tap or coupling.

[0010] Furthermore, the first metal strip (1) of each planar resonator in the planar bandpass filter may be on the left side of the second metal strip (2) or on the right side of the second metal strip (2).

[0011] Furthermore, the first metal strips (1) of all the planar resonators in the planar bandpass filter are on the same side of the second metal strip (2).

[0012] Furthermore, in two adjacent planar resonators in the planar bandpass filter, the first metal strip (1) of one planar resonator is on the left side of the second metal strip (2), and the first metal strip (1) of the other planar resonator is on the right side of the second metal strip (2).

[0013] Furthermore, when the input feeder (7) and the output feeder (8) are connected to the planar resonator in a coupled manner, the input feeder (7) and the output feeder (8) are in a "T" shape, the upper horizontal line of the "T" shape is parallel to the metal strip of the corresponding planar resonator, and the lower "1" shape faces outward, serving as an input or output port.

[0014] Furthermore, the impedance of the input feeder (7) and the output feeder (8) is 50 ohms.

[0015] The design of the new structure planar filter proposed in the present invention is suitable for microstrip circuits, stripline circuits and suspended microstrip circuits, such as Figure 6 The present invention reduces the inherent volume of the planar filter, realizes miniaturized design, and further introduces transmission zeros through cross-coupling between resonators, thereby improving frequency selectivity and achieving a higher level of stopband suppression to meet applications in more occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a circuit diagram of a single planar resonator of the present invention.

[0017] Figure 2 This is a circuit diagram of a tapped interdigital planar bandpass filter according to the present invention.

[0018] Figure 3 The circuit diagram of the coupled interdigital planar bandpass filter of the present invention is shown in FIG.

[0019] Figure 4 This is a circuit diagram of a tapped comb-type planar bandpass filter according to the present invention.

[0020] Figure 5 This is a circuit diagram of a coupled comb-type planar bandpass filter according to the present invention.

[0021] Figure 6 These are cross-sectional structural diagrams of three planar circuits suitable for the present invention.

[0022] Figure 7 This is a physical diagram of a fourth-order tapped interdigital microstrip bandpass filter that is specifically implemented in the present invention.

[0023] Figure 8 This is a test data diagram of a tapped interdigital microstrip bandpass filter specifically implemented in the present invention, wherein the horizontal axis is frequency in GHz, the vertical axis is S parameter in dB, the dotted line is the reflection S11 curve, and the solid line is the transmission S21 curve.

[0024] In the figure, 1-first metal strip, 2-second metal strip, 3-upper metal grounding strip, 4-lower metal grounding strip, 5-internal coupling gap of a single resonator, 6-metallized via, 7-input feed line, 8-output feed line. DETAILED DESCRIPTION

[0025] The technical solution of the present invention adopts a planar resonator with a new structure to construct a planar microwave bandpass filter. Figure 1 As shown, the proposed resonator is composed of two sections of metal strip lines, one end of which is open-circuited and the other end is short-circuited to the ground. Each metal strip line is of equal length, and the initial length is set to 1 / 4λ. The two sections of metal strip lines are relatively staggered and placed, and coupling is generated through the gap between them. Most of the positions of the resonators are overlapped, and the capacitance loading effect formed by the gap coupling can shorten the overall length of the resonator, so its overall length should be less than 1v4λ. If the coupling gap is smaller, the width of the metal strip line is narrower and the more overlapping parts are, the stronger the coupling effect is, resulting in a shorter resonator length. In theory, the maximum length of the resonator can be close to 1 / 12λ; as shown in FIG. Figure 2-Figure 5 As shown in the figure, the proposed planar bandpass filter circuit consists of multiple planar resonators, input / output feed lines, and upper and lower metal ground strips. According to the feeding method of the input / output feed lines and the arrangement of the planar resonator positions, four different circuit structures can be formed:

[0026] 1. Tapped interdigital type: Its circuit is as follows Figure 2 As shown, the input / output feed lines are connected to the first and last resonators in a tapped manner, and the positions of the resonators at each level are arranged in a centrally symmetrical manner with respect to the geometric center of the filter;

[0027] 2. Coupled interdigital type, its circuit is as follows Figure 3 As shown, the input / output feed lines are connected to the first and last resonators in a coupled manner, and the positions of the resonators at each level are arranged in a centrally symmetrical manner with respect to the geometric center of the filter;

[0028] 3. Tap-type comb type, its circuit is as follows Figure 4 As shown, the input / output feed lines are connected to the resonators at the head and tail in a tapped manner, and the positions of the resonators at each level are arranged in a mirror-symmetrical manner with respect to the geometric center of the filter;

[0029] 4. Coupled comb type, its circuit is as follows Figure 5 As shown, the input / output feed lines are connected to the head and tail resonators in a coupled manner, and the positions of the resonators at each stage are arranged in a mirror-symmetrical manner with respect to the geometric center of the filter.

[0030] Among them, the tap circuit can produce a stronger coupling effect than the coupled circuit, which is suitable for the design of broadband filters, while the interdigital circuit can produce a stronger coupling effect than the comb circuit, which is also suitable for the design of broadband filters. On the contrary, if the design is for a narrowband filter, the coupled and comb circuit designs can make the filter more compact.

[0031] Compared with conventional planar bandpass filters, the proposed planar bandpass filter has the following advantages:

[0032] 1. Conventional planar filters generally use resonators with open ends, and their length is 1 / 2λ, while the resonator length of the planar filter is 1 / 4λ to 1 / 12λ, so the miniaturization design of the filter can be realized;

[0033] 2. As the resonator is shortened, the parasitic passband of the filter it forms will be pulled to the farther end of the spectrum, which can achieve wider stopband suppression, causing the spurious frequency to be far away from the basic resonant frequency;

[0034] 3. Since one end of the resonator is connected to the metal grounding strip, non-adjacent resonators are connected through the metal grounding strip to form a second coupling path, thereby generating cross-coupling. Therefore, the upper stopband edge of the constructed filter will introduce a proximal transmission zero point, thereby improving the stopband steepness and stopband depth, and obtaining better filtering characteristics; or a filter with fewer orders can be used to achieve the desired filtering characteristics, thereby reducing the in-band insertion loss of the filter.

[0035] The present invention is a planar resonator with a new structure, characterized in that the circuit is etched on the metal layer on the surface of the circuit substrate, and the circuit structure of each resonator is: two metal strip lines of equal length and length of 1 / 4λ to 1 / 12λ are relatively staggered and placed, and a planar resonator is formed by coupling through the gap between the two. One end of the metal strip line is open circuit, and the other end is connected to the metal ground strip to achieve short circuit with the ground. The metal ground strip passes through the circuit substrate through a plurality of metallized vias and is connected to the metal ground on the back of the circuit.

[0036] According to the feeding method of the input / output feed line and the arrangement method of the resonator position, four types of planar bandpass filter circuits can be formed: tapped interdigital filter circuit, coupled interdigital filter circuit, tapped comb filter circuit and coupled comb filter circuit. Among them, the tapped interdigital filter circuit is most suitable for the design of broadband filters, while the coupled comb filter circuit is most suitable for the design of narrowband filters.

[0037] The actual picture of making a fourth-order microstrip bandpass filter is as follows Figure 7As shown. The circuit is placed in a metal cavity, and the connector is connected to the input / output feeder through the metal cavity. The circuit substrate is Rogers5880, with a thickness of 0.254mm. The circuit adopts a tapped interdigital type, etched on the metal layer on the surface of the circuit substrate, and the circuit size is 10mm×6.4mm. The test curve is shown as Figure 8 As shown, the center frequency is 14.2 GHz, the operating bandwidth is 400 MHz, the in-band reflection is better than 18 dB, the out-of-band suppression is greater than 30 dB @ 10 GHz ~ 13 GHz & 14.8 GHz ~ 25.2 GHz, and a transmission zero point appears at 15.2 GHz.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A planar resonator, the resonator comprising: A first metal strip (1), a second metal strip (2), an upper metal grounding strip (3), and a lower metal grounding strip (4); the upper metal grounding strip and the lower metal grounding strip (4) are arranged in parallel, the first metal strip (1) and the second metal strip (2) are arranged in parallel and are located between the upper metal grounding strip and the lower metal grounding strip (4), one end of the first metal strip (1) is connected to the upper metal grounding strip (3), and the other end is vacant; one end of the second metal strip (2) is connected to the lower metal grounding strip (4), and the other end is vacant; the overall length of the coupling structure formed by the first metal strip (1) and the second metal strip (2) is 14λ112λ, where λ is the waveguide wavelength of the resonant frequency of the resonator.

2. A planar resonator as claimed in claim 1, characterized in that: The upper metal grounding strip (3) and the lower metal grounding strip (4) are grounded via metallized vias (6).

3. A planar bandpass filter using the planar resonator as claimed in claim 1, the filter comprising: A plurality of planar resonators, an input feeder (7), and an output feeder (8), each planar resonator shares a same upper metal grounding strip (3) and a same lower metal grounding strip (4), and the upper metal grounding strip (3) is parallel to the lower metal grounding strip (4); the input feeder (7) is connected to the first-stage planar resonator by means of a tap or coupling, and the output feeder (8) is connected to the last-stage planar resonator by means of a tap or coupling.

4. The planar bandpass filter according to claim 3, characterized in that The input feed line (7) is connected to the metal strip outside the first-stage planar resonator by means of a tap or coupling, and the output feed line (8) is connected to the metal strip outside the last-stage planar resonator by means of a tap or coupling.

5. The planar bandpass filter according to claim 3, characterized in that: The first metal strip (1) of each planar resonator may be on the left side of the second metal strip (2) or on the right side of the second metal strip (2).

6. The planar bandpass filter according to claim 3, characterized in that: When the input feeder (7) and the output feeder (8) are connected to the planar resonator in a coupled connection, the input feeder (7) and the output feeder (8) are in a "T" shape, the upper horizontal line of the "T" shape is parallel to the metal strip of the corresponding planar resonator, and the lower "1" shape faces outwards, serving as an input or output port.

7. The planar bandpass filter according to claim 3, characterized in that: The impedance of the input feeder (7) and the output feeder (8) is 50 ohms.

8. The planar bandpass filter according to claim 5, characterized in that The first metal strips (1) of all planar resonators in the planar bandpass filter are on the same side of the second metal strips (2).

9. The planar bandpass filter according to claim 5, characterized in that: In two adjacent planar resonators, the first metal strip (1) of one planar resonator is on the left side of the second metal strip (2), and the first metal strip (1) of the other planar resonator is on the right side of the second metal strip (2).

10. Applying the planar bandpass filter as claimed in claims 3 to 9 to a microstrip circuit, a stripline circuit or a suspended microstrip circuit.

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